Power distribution network complex fault detection method and device and power distribution system

Abstract

The invention provides a power distribution network complex fault detection method and device and a power distribution system, and relates to the technical field of power systems. The power distribution network complex fault detection method comprises the following steps: determining power distribution lines with opposite polarities in a polar relation as single-phase earth fault lines, and determining power distribution lines with the same polarities in the polar relation as sound lines; when the power frequency current is greater than a current threshold value and the power frequency voltage is smaller than a second voltage threshold value, and a first circuit breaker and a second circuit breaker in the at least two circuit breakers execute a timed tripping action, determining that the distribution line is in an interphase short-circuit fault; and determining a power distribution section between the first circuit breaker and the second circuit breaker as an interphase short circuit fault section. According to the invention, reliable diagnosis of two-point secondary complex faults of the power distribution system is realized, and subsequent rapid isolation and recovery of single-phase earth faults and interphase short-circuit faults are facilitated.

Description

Technical Field

[0001] The present application relates to the technical field of power systems, and in particular to a method and device for detecting complex faults in a distribution network, and a distribution system. Background Art

[0002] The construction of a new power system that integrates distributed photovoltaic and other new energy sources is an important task for the country. Among them, the distribution network is the key link between the transmission network and users, and plays an important role in the reliability and safe and stable operation of the power system.

[0003] Affected by extreme weather conditions such as lightning, typhoons, and rainstorms, distribution networks are prone to failure. According to statistics, the probability of distribution network failure is relatively high, accounting for more than 70% of the total power grid failure events. Among them, the probability of distribution line failure accounts for about 90% of the total distribution network failure. If the distribution line failure is not diagnosed and handled in a timely manner, it will cause personal injury, property loss, electrical fire and other hazards in serious cases.

[0004] In the related technologies, the research on distribution network fault diagnosis is mainly carried out on single simple faults. However, the actual distribution line faults have new characteristics of secondary and complexity, which brings new challenges to fault diagnosis research. Therefore, in order to ensure the safe and stable operation of the distribution network, the research on the diagnosis of secondary complex faults at two points in the distribution line is of great importance. Summary of the invention

[0005] The present application aims to solve one of the technical problems existing in the prior art or related technology.

[0006] To this end, the first aspect of the present application proposes a method for detecting complex faults in a distribution network.

[0007] A second aspect of the present application provides a complex fault detection device for a distribution network.

[0008] A third aspect of the present application provides a complex fault detection device for a distribution network.

[0009] A fourth aspect of the present application provides a power distribution system.

[0010] In view of this, according to the first aspect of the present application, a method for detecting complex faults in a distribution network is proposed, which is applied to a distribution system. The distribution system includes at least two distribution lines, and each distribution line includes at least two circuit breakers. The method for detecting complex faults in a distribution network includes: when the zero-sequence voltage of the distribution system is greater than a first voltage threshold, obtaining voltage traveling waves and current traveling waves in at least two distribution lines; determining the polarity relationship between the voltage traveling wave and the current traveling wave in each distribution line; determining a distribution line with opposite polarity as a single-phase grounding fault line, and determining a distribution line with the same polarity as a sound line; in the distribution system When the zero-sequence voltage is less than or equal to a first voltage threshold, the power frequency current and power frequency voltage in at least two distribution lines and the action information of at least two circuit breakers are obtained; when the power frequency current is greater than the current threshold and the power frequency voltage is less than the second voltage threshold, and the first circuit breaker and the second circuit breaker of at least two circuit breakers perform a timed tripping action, it is determined that the distribution line is in a phase-to-phase short circuit fault; the distribution section between the first circuit breaker and the second circuit breaker is determined as a phase-to-phase short circuit fault section, wherein the first circuit breaker is a circuit breaker close to the power supply side of the phase-to-phase short circuit fault section, and the second circuit breaker is a circuit breaker close to the load side of the phase-to-phase short circuit fault section.

[0011] In the technical solution of the present application, for secondary single-phase grounding faults and phase-to-phase short-circuit faults, by continuously collecting voltage waves, current waves, power frequency voltage, power frequency current and relay action information on the distribution line, and based on the voltage waves and current waves, the single-phase grounding fault can be identified and located, and the phase-to-phase short-circuit fault can be identified and located based on the power frequency voltage, power frequency current and circuit breaker action information, thereby achieving reliable diagnosis of secondary complex faults at two points in the distribution system, and facilitating the subsequent rapid isolation and recovery of single-phase grounding faults and phase-to-phase short-circuit faults.

[0012] In some technical schemes, optionally, the first circuit breaker and the second circuit breaker of at least two circuit breakers perform a timed tripping action, including: when the power frequency current is greater than the current threshold and the power frequency voltage is less than the second voltage threshold, the first circuit breaker trips after a delay of a preset time; after the first circuit breaker trips after a delay of a preset time, the second circuit breaker trips.

[0013] In this technical solution, under the action of time-limited overcurrent protection, when it is detected that the power frequency current is greater than the current threshold and the power frequency voltage is less than the second voltage threshold, the first circuit breaker on the power supply side trips after a delay of a preset time, and the second circuit breaker on the opposite load side accelerates the tripping action after the first circuit breaker trips.

[0014] Specifically, after collecting the action information of the first circuit breaker delaying the tripping action for a preset time and the second circuit breaker accelerating the tripping action, combined with the fact that the power frequency current is greater than the current threshold and the power frequency voltage is less than the second voltage threshold, it can be determined that the section between the first circuit breaker and the second circuit breaker is a phase-to-phase short circuit fault section.

[0015] In the technical solution of the present application, by collecting the action information of the circuit breaker, and when the action information that meets the first circuit breaker delay preset time tripping action and the second circuit breaker accelerated tripping action is collected, the phase-to-phase short-circuit fault section can be accurately identified based on the action information, thereby improving the positioning accuracy of the phase-to-phase short-circuit fault section.

[0016] In some technical solutions, optionally, the preset time lengths of the action delays of at least two circuit breakers from the load side to the power side are increased sequentially.

[0017] In this technical solution, in order to meet the selectivity requirement, the action time setting value of each circuit breaker in the time-limited overcurrent protection presents a step-type time characteristic. Therefore, the phase-to-phase short circuit fault section in the distribution line can be determined based on the action time of the first circuit breaker and the second circuit breaker.

[0018] In the technical solution of the present application, by setting the preset duration of the delayed action of each relay in the power distribution system, when collecting the circuit breaker action information, the first circuit breaker on the power supply side of the phase-to-phase short-circuit fault section can be accurately located, and the second circuit breaker on the load side of the phase-to-phase short-circuit fault section can be located, so that the phase-to-phase short-circuit fault section can be located according to the action information of the circuit breaker, which facilitates the subsequent isolation and processing of the phase-to-phase short-circuit fault section.

[0019] In some technical schemes, optionally, after determining the distribution lines with opposite polarity relationships as single-phase grounding fault lines, and determining the distribution lines with the same polarity relationships as sound lines, the distribution network complex fault detection method also includes: obtaining the arrival time of the initial fault traveling wave reaching each circuit breaker in the single-phase grounding fault line; and determining the single-phase grounding fault section in the single-phase grounding fault line based on the arrival time.

[0020] In this technical solution, a measuring device is correspondingly arranged at each circuit breaker position on the distribution line. After detecting the initial fault wave, the measuring device can record the arrival time of the initial fault wave at the circuit breaker position. According to the arrival time of the initial fault wave at each circuit breaker position, the single-phase-to-ground phase-to-phase short circuit fault section can be located.

[0021] It should be noted that the fault initial traveling wave includes the fault initial voltage traveling wave and the fault initial current traveling wave.

[0022] Specifically, according to the arrival time at each circuit breaker position, the distance between each circuit breaker and the fault point can be determined, and the fault point can be located according to the distance between each circuit breaker and the fault point, thereby determining the single-phase to ground phase-to-phase short circuit fault section where the fault point is located.

[0023] In the technical solution of the present application, after a single-phase grounding fault line is detected, the single-phase grounding fault point can be located according to the arrival time of the initial fault traveling wave at each circuit breaker position in the single-phase grounding fault line, thereby accurately determining the single-phase grounding phase-to-phase short-circuit fault section, which is convenient for subsequent isolation and processing of the single-phase grounding phase-to-phase short-circuit fault section.

[0024] In some technical solutions, optionally, determining the polarity relationship between the voltage traveling wave and the current traveling wave in each distribution line includes:

[0025] When the voltage traveling wave and the current traveling wave satisfy the first relational expression, it is determined that the polarity relationship between the voltage traveling wave and the current traveling wave is opposite, and the first relational expression includes:

[0026]

[0027] Among them, i Fα 、i Fβ are the initial line mode current traveling waves on the single-phase grounding fault line, i F0 is the initial zero-mode current traveling wave on the single-phase grounding fault line, u Fα 、u Fβ They are all the initial line mode voltage traveling waves on the single-phase grounding fault line, u F0 is the initial zero-mode voltage traveling wave on the single-phase grounding fault line, n is the number of lines, R f is the transition resistance, u AF is the voltage at the fault point before the fault occurs, Z α is the traveling wave impedance of the line mode, and Z0 is the traveling wave impedance of the zero mode.

[0028] In the technical solution of the present application, after collecting the voltage wave and the current wave on the distribution line, it is determined whether the voltage wave and the current wave satisfy the above-mentioned first relationship. When the above-mentioned first relationship is satisfied, it is determined that the polarity of the voltage wave and the current wave is opposite, that is, the distribution line is a single-phase grounding fault line.

[0029] In some technical solutions, optionally, determining the polarity relationship between the voltage traveling wave and the current traveling wave in each distribution line includes:

[0030] When the voltage traveling wave and the current traveling wave satisfy the second relational expression, it is determined that the polarity relationship between the voltage traveling wave and the current traveling wave is the same, and the second relational expression includes:

[0031]

[0032] Among them, i Nα 、i Nβ are the initial line mode current traveling waves on a sound line, i N0 is the initial zero-mode current traveling wave on a sound line, u Nα 、u Nβ are the initial line mode voltage traveling waves on a sound line, u N0 is the initial zero-mode voltage traveling wave on a sound line, n is the number of lines, R f is the transition resistance, u AF is the voltage at the fault point before the fault occurs, Z α is the traveling wave impedance of the line mode, and Z0 is the traveling wave impedance of the zero mode.

[0033] In the technical solution of the present application, after collecting the voltage wave and the current wave on the distribution line, it is determined whether the voltage wave and the current wave satisfy the above-mentioned second relationship. When the above-mentioned second relationship is satisfied, it is determined that the polarity of the voltage wave and the current wave is the same, that is, the distribution line is a sound line without a single-phase grounding fault.

[0034] In some technical solutions, optionally, the value range of the first voltage threshold is 5% to 15% of the rated voltage value.

[0035] In this technical solution, the first voltage threshold is a voltage threshold determined according to the rated voltage value of the distribution system, and can be specifically selected to be greater than or equal to 5% of the rated voltage value and less than or equal to 15% of the rated voltage value. Based on this first voltage threshold, it is possible to accurately determine whether a single-phase grounding fault may exist in the distribution line.

[0036] According to a second aspect of the present application, a distribution network complex fault detection device is proposed, which is applied to a distribution system. The distribution system includes at least two distribution lines, each distribution line includes at least two circuit breakers, and the distribution network complex fault detection device includes: an acquisition module, which is used to acquire voltage traveling waves and current traveling waves in at least two distribution lines when the zero-sequence voltage of the distribution system is greater than a first voltage threshold; a determination module, which is used to determine the polarity relationship between the voltage traveling wave and the current traveling wave in each distribution line; the determination module is also used to determine the distribution line with opposite polarity as a single-phase grounding fault line, and determine the distribution line with the same polarity as a sound line; the acquisition module is also used to When the zero-sequence voltage of the distribution system is less than or equal to the first voltage threshold, the power frequency current and power frequency voltage in at least two distribution lines and the action information of at least two circuit breakers are obtained; the determination module is also used to determine that the distribution line is in a phase-to-phase short circuit fault when the power frequency current is greater than the current threshold and the power frequency voltage is less than the second voltage threshold, and the first circuit breaker and the second circuit breaker of at least two circuit breakers perform a timed tripping action; the determination module is also used to determine the distribution section between the first circuit breaker and the second circuit breaker as a phase-to-phase short circuit fault section, wherein the first circuit breaker is the circuit breaker close to the power supply side of the phase-to-phase short circuit fault section, and the second circuit breaker is the circuit breaker close to the load side of the phase-to-phase short circuit fault section.

[0037] In the technical solution of the present application, for secondary single-phase grounding faults and phase-to-phase short-circuit faults, by continuously collecting voltage waves, current waves, power frequency voltage, power frequency current and relay action information on the distribution line, and based on the voltage waves and current waves, the single-phase grounding fault can be identified and located, and the phase-to-phase short-circuit fault can be identified and located based on the power frequency voltage, power frequency current and circuit breaker action information, thereby achieving reliable diagnosis of secondary complex faults at two points in the distribution system, and facilitating the subsequent rapid isolation and recovery of single-phase grounding faults and phase-to-phase short-circuit faults.

[0038] According to the third aspect of the present application, a distribution network complex fault detection device is proposed, the distribution network complex fault detection device includes a processor and a memory, the memory stores a program or instruction, and when the program or instruction is executed by the processor, the steps of the distribution network complex fault detection method in any of the above technical solutions are implemented. Therefore, the distribution network complex fault detection device has all the beneficial effects of the distribution network complex fault detection method in any of the above technical solutions, which will not be repeated here.

[0039] According to the fourth aspect of the present application, a power distribution system is proposed, comprising: at least two power distribution lines, arranged between a power source and a load, wherein each power distribution line is provided with at least two circuit breakers; a distribution network complex fault detection device, the distribution network complex fault detection device being arranged on the distribution line, the distribution network complex fault detection device being used to control the on / off state of the circuit breaker; and a master station, which is communicatively connected to the distribution network complex fault detection device. Since the distribution network complex fault detection device is the distribution network complex fault detection device in any of the above technical solutions, it has all the technical effects of the distribution network complex fault detection device in any of the above technical solutions, which will not be described in detail here.

[0040] Additional aspects and advantages of the present application will become apparent in the following description or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0042] Figure 1 One of the flow charts of a complex fault detection method for a distribution network provided in some embodiments of the present application is shown;

[0043] Figure 2 A schematic diagram of a power distribution system provided in some embodiments of the present application is shown;

[0044] Figure 3 A waveform diagram of the action time limit setting value in an embodiment of the present application is shown;

[0045] Figure 4 A second flowchart of a method for detecting complex faults in a distribution network provided in some embodiments of the present application is shown;

[0046] Figure 5 One of the structural block diagrams of a complex fault detection device for a power distribution network is shown in some embodiments of the present application;

[0047] Figure 6 A second structural block diagram of a complex fault detection device for a distribution network provided in some embodiments of the present application is shown.

[0048] The reference numerals are as follows:

[0049] 200 distribution system, 201 power supply, 202 distribution line, 203 load, 204 circuit breaker, 205 master station, 500 complex fault detection device of distribution network. DETAILED DESCRIPTION

[0050] In order to more clearly understand the above-mentioned objectives, features and advantages of the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, in the absence of conflict, the present embodiment and the features in the embodiment can be combined with each other.

[0051] In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present application is not limited to the specific embodiments disclosed below.

[0052] Refer to the following Figures 1 to 6 A method, device and system for detecting complex faults in a power distribution network according to some embodiments of the present application are described.

[0053] According to one embodiment of the present application, a complex fault detection method for a distribution network is proposed, which is applied to a distribution system, wherein the distribution system includes at least two distribution lines, each of which includes at least two circuit breakers. Figure 1 One of the flow charts of a complex fault detection method for a distribution network provided in some embodiments of the present application is shown. Figure 2 A schematic diagram of a power distribution system provided in some embodiments of the present application is shown. Figure 2 As shown, in this embodiment, the complex fault detection method of the distribution network is applied to the distribution system, which includes at least two distribution lines, and the distribution lines are connected between the power supply and the load. At least two circuit breakers are arranged on each distribution line, and at least two circuit breakers divide the distribution line into multiple distribution sections, and a distribution section is formed between two adjacent circuit breakers.

[0054] like Figure 2 As shown, the power distribution system 200 includes two power distribution lines 202, and a plurality of circuit breakers 204 are arranged on each power distribution line 202. A measuring device is also arranged at the position of each circuit breaker 204, and the measuring device is used to collect the measurement parameters at the circuit breaker 204. The measurement parameters include but are not limited to the power frequency voltage, power frequency current, current traveling wave, voltage traveling wave, etc.

[0055] like Figure 1 As shown, the complex fault detection method of the distribution network includes:

[0056] Step 102, when the zero-sequence voltage of the power distribution system is greater than a first voltage threshold, obtaining voltage traveling waves and current traveling waves in at least two distribution lines;

[0057] In this embodiment, when the zero-sequence voltage of the power distribution system is greater than the first voltage threshold, it is determined that there may be a single-phase grounding fault in the power distribution system. At this time, it is necessary to determine the single-phase grounding fault line in the power distribution line that is in a single-phase grounding fault state and the healthy line without fault according to the voltage traveling wave and current traveling wave on each distribution line. Wherein, a corresponding measuring device is provided at the position of each circuit breaker, and the current traveling wave and voltage traveling wave at the corresponding position can be directly collected through the measuring device.

[0058] Specifically, after a single-phase grounding fault occurs in a distribution line, the voltage at the fault point drops, which is equivalent to superimposing an additional power source at the fault point with a voltage direction opposite to that at the point in a normal state. This power source generates traveling waves that propagate to both ends of the line. Therefore, the collected voltage and current traveling waves can be used to determine whether a single-phase grounding fault occurs in the distribution line.

[0059] Step 104, determining the polarity relationship between the voltage traveling wave and the current traveling wave in each distribution line;

[0060] Step 106, determining the distribution lines with opposite polarity as single-phase grounding fault lines, and determining the distribution lines with the same polarity as sound lines;

[0061] In this embodiment, when a single-phase grounding fault occurs in the distribution system, since the distribution system includes multiple distribution lines, it is necessary to first locate the distribution line where the single-phase grounding fault occurs. After locating the distribution line where the single-phase grounding fault occurs, the single-phase grounding phase-to-phase short-circuit fault section in the distribution line with the single-phase grounding fault can be located, and the single-phase grounding phase-to-phase short-circuit fault section can be processed accordingly in a timely manner.

[0062] Specifically, since the polarities of the fault initial current wave and the fault initial voltage wave of the single-phase grounding fault line are opposite, and the polarities of the fault initial current wave and the fault initial voltage wave of the healthy line are the same, based on this characteristic difference, the single-phase grounding fault line in at least two distribution lines and the healthy line in at least two distribution lines can be determined by identifying the polarities of the collected current wave and voltage wave on the distribution line.

[0063] Step 108, when the zero-sequence voltage of the power distribution system is less than or equal to the first voltage threshold, obtaining power frequency current and power frequency voltage in at least two distribution lines, and operation information of at least two circuit breakers;

[0064] In this embodiment, when the zero-sequence voltage in the power distribution system is less than or equal to the first voltage threshold, it is determined that there may be no single-phase grounding fault in the power distribution system. Therefore, it is necessary to detect whether there is an interphase short circuit fault in the power distribution system. By detecting the power frequency voltage, power frequency current and action information of each circuit breaker in the power distribution system through the measuring device, it is possible to detect whether there is an interphase short circuit fault in the power distribution system.

[0065] Specifically, the time-limited overcurrent protection is a protection that avoids the maximum load current setting according to the setting current. It does not start when the distribution network is operating normally, but it can respond to the increase of current and start when a phase-to-phase short circuit fault occurs in the distribution line. Therefore, by monitoring the power frequency voltage, power frequency current and circuit breaker operation information, it is possible to determine whether there is a phase-to-phase short circuit fault in the distribution system.

[0066] Step 110, when the power frequency current is greater than the current threshold, the power frequency voltage is less than the second voltage threshold, and the first circuit breaker and the second circuit breaker of at least two circuit breakers perform a timed tripping action, it is determined that the distribution line is in a phase-to-phase short circuit fault;

[0067] In this embodiment, when an interphase short circuit fault occurs, the power frequency current increases and the power frequency voltage drops rapidly, and under the action of the time-limited overcurrent protection, the circuit breakers at both ends of the interphase short circuit fault section trip successively. Therefore, after the power frequency current is greater than the current threshold, the power frequency voltage is less than the second voltage threshold, and the first relay and the second relay at both ends of the interphase short circuit fault section trip successively, it is determined that the distribution line is in an interphase short circuit fault.

[0068] Specifically, the current threshold is the starting current setting value of the definite time overcurrent protection, and the expression of the current threshold is as follows:

[0069]

[0070] Among them, I set is the starting current setting value of the time-limited overcurrent protection, that is, the current threshold, K re I is the return coefficient of the current relay, which is generally 0.85 for electromechanical relays and 0.9-0.95 for static relays. re is the return current of protection, K rel K is the reliability coefficient, which is generally between 1.25 and 1.5. Ms I is the self-starting coefficient of the motor, which is greater than 1. The specific value is determined by the specific network wiring and load properties of the distribution system. L.max It is the maximum load current during normal operation of the power distribution system.

[0071] Step 112, determining the distribution section between the first circuit breaker and the second circuit breaker as a phase-to-phase short circuit fault section, wherein the first circuit breaker is the circuit breaker close to the power supply side of the phase-to-phase short circuit fault section, and the second circuit breaker is the circuit breaker close to the load side of the phase-to-phase short circuit fault section.

[0072] In this embodiment, if a phase-to-phase short circuit fault occurs in the distribution line, the fault power frequency voltage is greatly reduced and the current increases, which may exceed the starting current setting value of the time-limited overcurrent protection, causing the first circuit breaker on the power supply side to trip first. After the first circuit breaker on the power supply side is actuated, the healthy phase current will suddenly change, and the second circuit breaker on the load side of the phase-to-phase short circuit fault section will trip faster. Therefore, the phase-to-phase short circuit fault section is identified based on the power frequency voltage and current change characteristics after the fault and the circuit breaker action information on both sides.

[0073] In the embodiments of the present application, for secondary single-phase grounding faults and phase-to-phase short-circuit faults, by continuously collecting voltage waves, current waves, power frequency voltage, power frequency current and relay action information on the distribution line, and based on the voltage waves and current waves, the single-phase grounding fault can be identified and located, and the phase-to-phase short-circuit fault can be identified and located based on the power frequency voltage, power frequency current and circuit breaker action information, thereby achieving reliable diagnosis of secondary complex faults at two points in the distribution system, and facilitating subsequent rapid isolation and recovery of single-phase grounding faults and phase-to-phase short-circuit faults.

[0074] In some embodiments, optionally, the first circuit breaker and the second circuit breaker of at least two circuit breakers perform a timed tripping action, including: when the power frequency current is greater than a current threshold and the power frequency voltage is less than a second voltage threshold, the first circuit breaker trips after a delay of a preset time; after the first circuit breaker trips after a delay of a preset time, the second circuit breaker trips.

[0075] In this embodiment, under the action of the time-limited overcurrent protection, when it is detected that the power frequency current is greater than the current threshold and the power frequency voltage is less than the second voltage threshold, the first circuit breaker on the power supply side trips after a delay of a preset time length, and the second circuit breaker on the opposite load side accelerates the tripping action after the first circuit breaker trips.

[0076] Specifically, after collecting the action information of the first circuit breaker delaying the tripping action for a preset time and the second circuit breaker accelerating the tripping action, combined with the fact that the power frequency current is greater than the current threshold and the power frequency voltage is less than the second voltage threshold, it can be determined that the section between the first circuit breaker and the second circuit breaker is a phase-to-phase short circuit fault section.

[0077] In an embodiment of the present application, by collecting the action information of the circuit breaker, and when the action information that meets the first circuit breaker delay preset time tripping action and the second circuit breaker accelerated tripping action is collected, the phase-to-phase short-circuit fault section can be accurately identified based on the action information, thereby improving the positioning accuracy of the phase-to-phase short-circuit fault section.

[0078] In some embodiments, optionally, the preset time lengths of the action delays of at least two circuit breakers from the load side to the power side are increased sequentially.

[0079] In this embodiment, in order to meet the selectivity requirement, the action time setting value of each circuit breaker in the time-limited overcurrent protection presents a step-type time characteristic. Therefore, the phase-to-phase short circuit fault section in the distribution line can be determined according to the action time of the first circuit breaker and the second circuit breaker.

[0080] Figure 3 The waveform diagram of the action time limit setting value in the embodiment of the present application is shown as follows: Figure 3 As shown, k represents the fault, Δt is the time difference, l is the distance, and t is the time. The relationship between the protection action time limits of each circuit breaker is t2=t1+Δt, t3=t2+Δt, t4=t3+Δt. The action time limit of the time-limited overcurrent protection has nothing to do with the magnitude of the short-circuit current. The closer to the power supply side, the longer the action time limit. That is, the circuit breaker close to the load side trips first, and the circuit breaker close to the power supply side trips later.

[0081] In an embodiment of the present application, by setting a preset duration of the delayed action of each relay in the power distribution system, when collecting circuit breaker action information, the first circuit breaker on the power supply side of the phase-to-phase short-circuit fault section can be accurately located, and the second circuit breaker on the load side of the phase-to-phase short-circuit fault section can be located, so that the phase-to-phase short-circuit fault section can be located according to the action information of the circuit breaker, which facilitates the subsequent isolation and processing of the phase-to-phase short-circuit fault section.

[0082] In some embodiments, optionally, after determining the distribution lines with opposite polarity relationships as single-phase grounding fault lines, and determining the distribution lines with the same polarity relationships as sound lines, the distribution network complex fault detection method also includes: obtaining the arrival time of the initial fault traveling wave reaching each circuit breaker in the single-phase grounding fault line; and determining the single-phase grounding fault section in the single-phase grounding fault line based on the arrival time.

[0083] In this embodiment, a measuring device is provided at each circuit breaker position on the distribution line. After detecting the initial fault wave, the measuring device can record the arrival time of the initial fault wave at the circuit breaker position. According to the arrival time of the initial fault wave at each circuit breaker position, the single-phase-to-ground phase-to-phase short circuit fault section can be located.

[0084] It should be noted that the fault initial traveling wave includes the fault initial voltage traveling wave and the fault initial current traveling wave.

[0085] Specifically, according to the arrival time at each circuit breaker position, the distance between each circuit breaker and the fault point can be determined, and the fault point can be located according to the distance between each circuit breaker and the fault point, thereby determining the single-phase to ground phase-to-phase short circuit fault section where the fault point is located.

[0086] In an embodiment of the present application, after a single-phase grounding fault line is detected, the single-phase grounding fault point can be located according to the arrival time of the initial fault traveling wave at each circuit breaker position in the single-phase grounding fault line, thereby accurately determining the single-phase grounding phase-to-phase short-circuit fault section, which facilitates the subsequent isolation and processing of the single-phase grounding phase-to-phase short-circuit fault section.

[0087] In some embodiments, optionally, determining the polarity relationship between the voltage traveling wave and the current traveling wave in each distribution line includes:

[0088] When the voltage traveling wave and the current traveling wave satisfy the first relational expression, it is determined that the polarity relationship between the voltage traveling wave and the current traveling wave is opposite, and the first relational expression includes:

[0089]

[0090] Among them, i Fα 、i Fβ are the initial line mode current traveling waves on the single-phase grounding fault line, i F0 is the initial zero-mode current traveling wave on the single-phase grounding fault line, u Fα 、u Fβ They are all the initial line mode voltage traveling waves on the single-phase grounding fault line, u F0 is the initial zero-mode voltage traveling wave on the single-phase grounding fault line, n is the number of lines, R f is the transition resistance, u AF is the voltage at the fault point before the fault occurs, Z α is the traveling wave impedance of the line mode, and Z0 is the traveling wave impedance of the zero mode.

[0091] In an embodiment of the present application, after collecting the voltage wave and the current wave on the distribution line, it is determined whether the voltage wave and the current wave satisfy the above-mentioned first relationship. When the above-mentioned first relationship is satisfied, it is determined that the polarity of the voltage wave and the current wave is opposite, that is, the distribution line is a single-phase grounding fault line.

[0092] In some embodiments, optionally, determining the polarity relationship between the voltage traveling wave and the current traveling wave in each distribution line includes:

[0093] When the voltage traveling wave and the current traveling wave satisfy the second relational expression, it is determined that the polarity relationship between the voltage traveling wave and the current traveling wave is the same, and the second relational expression includes:

[0094]

[0095] Among them, i Nα 、i Nβ are the initial line mode current traveling waves on a sound line, i N0 is the initial zero-mode current traveling wave on a sound line, u Nα 、u Nβ are the initial line mode voltage traveling waves on a sound line, u N0 is the initial zero-mode voltage traveling wave on a sound line, n is the number of lines, R f is the transition resistance, u AF is the voltage at the fault point before the fault occurs, Z α is the traveling wave impedance of the line mode, and Z0 is the traveling wave impedance of the zero mode.

[0096] In an embodiment of the present application, after collecting the voltage wave and the current wave on the distribution line, it is determined whether the voltage wave and the current wave satisfy the above-mentioned second relationship. When the above-mentioned second relationship is satisfied, it is determined that the polarity of the voltage wave and the current wave is the same, that is, the distribution line is a sound line without a single-phase grounding fault.

[0097] The polarity relationship between the voltage traveling wave and the current traveling wave is explained below:

[0098] The partial differential equations of the voltage u and current i of a single lossless distributed parameter line related to both the position x and the time t are shown in the following expression (4):

[0099]

[0100] Wherein, u is the voltage of a single lossless distributed parameter line, i is the current of a single lossless distributed parameter line, L is the inductance per unit length of the line, C is the capacitance per unit length of the line to ground, x is the position, and t is the time.

[0101] By differentiating expression (4), we obtain the wave equation (5):

[0102]

[0103] Wherein, u is the voltage of a single lossless distributed parameter line, i is the current of a single lossless distributed parameter line, L is the inductance per unit length of the line, C is the capacitance per unit length of the line to ground, x is the position, and t is the time.

[0104] Solving the wave equation (5) gives the expression (6) of the solution of the differential equation as follows:

[0105]

[0106] in, and are the forward and reverse traveling waves respectively. is the traveling wave speed, is the traveling wave impedance.

[0107] By using phase mode transformation, the three-phase lossless transposed line can be decomposed into three independent mode components: α, β, and 0. The expressions (7) of the impedance and wave velocity of each mode are as follows:

[0108]

[0109] Where L1 is the line mode inductance per unit length of the line, C1 is the line mode capacitance to ground per unit length of the line, L0 is the zero mode inductance per unit length of the line, C0 is the zero mode capacitance to ground per unit length of the line, and Z α and Z β is the traveling wave impedance of the line mode, Z0 is the traveling wave impedance of the zero mode, v α and v β is the traveling wave velocity of the line mode, and v0 is the traveling wave velocity of the zero mode.

[0110] The first relation (2) and the second relation (3) can be determined by the above-mentioned expression (7) of each mode impedance and wave velocity, thereby determining that the polarity of the fault initial current traveling wave and the fault initial voltage traveling wave of the fault line is opposite, while the polarity of the fault initial current traveling wave and the fault initial voltage traveling wave of the sound line is the same. Based on this characteristic difference, the fault line can be accurately identified.

[0111] In some embodiments, optionally, the value range of the first voltage threshold is 5% to 15% of the rated voltage value.

[0112] In this embodiment, the first voltage threshold is a voltage threshold determined according to the rated voltage value of the distribution system, and can be specifically selected to be greater than or equal to 5% of the rated voltage value and less than or equal to 15% of the rated voltage value. Based on this first voltage threshold, it is possible to accurately determine whether a single-phase grounding fault may exist in the distribution line.

[0113] Exemplarily, the value of the first voltage threshold is 10% of the rated voltage value.

[0114] Figure 4 FIG. 2 shows a flow chart of a method for detecting complex faults in a distribution network provided in some embodiments of the present application. Figure 4 As shown, the complex fault detection method of the distribution network includes:

[0115] Step 401, collecting voltage traveling wave, current traveling wave, power frequency voltage, power frequency current and circuit breaker action information;

[0116] Step 402, determine whether U0>10%U N If the judgment result is yes, execute step 403, otherwise execute step 408;

[0117] Step 403, extracting the current traveling wave and the voltage traveling wave of each distribution line;

[0118] Step 404, determining whether the current wave and the voltage wave have opposite polarities, if the determination result is yes, executing step 406, otherwise executing step 405;

[0119] Step 405, the power distribution line is a sound line;

[0120] Step 406, the power distribution line is a single-phase grounding fault line;

[0121] Step 407, determining the single-phase to ground phase short circuit fault section according to the arrival time of the initial fault traveling wave to each circuit breaker;

[0122] Step 408, extracting the power frequency voltage, power frequency current and circuit breaker action information;

[0123] Step 409, determining whether the time-limited overcurrent protection action triggers the circuit breaker to trip, if it is determined to be, executing step 410, otherwise returning to executing step 401;

[0124] Step 410, locating the phase-to-phase short circuit fault section according to the circuit breaker action information.

[0125] In an embodiment of the present application, after a single-phase grounding fault occurs in the distribution line, the voltage at the fault point drops, which is equivalent to superimposing an additional power source at the fault point with a voltage direction opposite to that of the point in the normal state. The power source generates a traveling wave that propagates to both ends of the line. According to the propagation characteristics of the fault traveling wave, the fault additional network is solved to obtain the equations of the fault initial voltage and current traveling waves on the fault line and the sound line, respectively. Based on the equation, it can be obtained that the polarity of the fault initial current traveling wave and the fault initial voltage traveling wave of the fault line are opposite, while the polarity of the fault initial current traveling wave and the fault initial voltage traveling wave of the sound line are the same. Combined with this fault characteristic difference, the single-phase grounding fault line can be accurately judged. The fault interval is determined by recording the time when the fault initial traveling wave reaches the section switch.

[0126] After a phase-to-phase short circuit occurs in the distribution line, the power frequency voltage drops rapidly, the power frequency current increases, the power frequency voltage is less than the voltage threshold of the time-limited overcurrent protection, and the power frequency current is greater than the current threshold of the time-limited overcurrent protection. According to the step-type action time limit characteristics of the protection, the first circuit breaker on the opposite power supply side trips first. According to the sudden change characteristics of the healthy phase current after the first circuit breaker is actuated, the second circuit breaker on the load side of this end trips faster. By detecting the changing characteristics of the power frequency voltage and power frequency current and the action information of the circuit breaker, the occurrence of the phase-to-phase short circuit fault can be accurately diagnosed and the fault interval can be identified.

[0127] According to one embodiment of the present application, Figure 5 One of the structural block diagrams of a complex fault detection device for a power distribution network is shown in some embodiments of the present application. Figure 5 As shown, a complex fault detection device 500 for a distribution network is proposed, which is applied to a distribution system. The distribution system includes at least two distribution lines, each of which includes at least two circuit breakers. The complex fault detection device 500 for a distribution network includes:

[0128] An acquisition module 502 is used to acquire voltage traveling waves and current traveling waves in at least two distribution lines when the zero-sequence voltage of the distribution system is greater than a first voltage threshold;

[0129] A determination module 504, for determining the polarity relationship between the voltage traveling wave and the current traveling wave in each distribution line;

[0130] The determination module 504 is further used to determine the distribution lines with opposite polarity as single-phase grounding fault lines, and determine the distribution lines with the same polarity as sound lines;

[0131] The acquisition module 502 is further used to acquire the power frequency current and power frequency voltage in at least two distribution lines and the action information of at least two circuit breakers when the zero sequence voltage of the power distribution system is less than or equal to the first voltage threshold;

[0132] The determination module 504 is further configured to determine that the distribution line is in a phase-to-phase short circuit fault when the power frequency current is greater than the current threshold, the power frequency voltage is less than the second voltage threshold, and the first circuit breaker and the second circuit breaker of at least two circuit breakers perform a timed tripping action;

[0133] The determination module 504 is also used to determine the distribution section between the first circuit breaker and the second circuit breaker as a phase-to-phase short circuit fault section, wherein the first circuit breaker is the circuit breaker close to the power supply side of the phase-to-phase short circuit fault section, and the second circuit breaker is the circuit breaker close to the load side of the phase-to-phase short circuit fault section.

[0134] In the embodiments of the present application, for secondary single-phase grounding faults and phase-to-phase short-circuit faults, by continuously collecting voltage waves, current waves, power frequency voltage, power frequency current and relay action information on the distribution line, and based on the voltage waves and current waves, the single-phase grounding fault can be identified and located, and the phase-to-phase short-circuit fault can be identified and located based on the power frequency voltage, power frequency current and circuit breaker action information, thereby achieving reliable diagnosis of secondary complex faults at two points in the distribution system, and facilitating subsequent rapid isolation and recovery of single-phase grounding faults and phase-to-phase short-circuit faults.

[0135] According to one embodiment of the present application, Figure 6 The second structural block diagram of a complex fault detection device for a power distribution network provided in some embodiments of the present application is shown. Figure 6 As shown, the complex fault detection device 600 for distribution network includes a processor 602 and a memory 604. The memory 604 stores a program or instruction. When the program or instruction is executed by the processor 602, the steps of the complex fault detection method for distribution network in any of the above embodiments are implemented. Therefore, the complex fault detection device 600 for distribution network has all the beneficial effects of the complex fault detection method for distribution network in any of the above embodiments, which will not be described in detail here.

[0136] According to one embodiment of the present application, optionally, a readable storage medium is provided, on which a program or instruction is stored. When the program or instruction is executed by a processor, the steps of the complex fault detection method for a distribution network as in any of the above-mentioned embodiments are implemented, thereby having all the beneficial technical effects of the complex fault detection method for a distribution network as in any of the above-mentioned embodiments.

[0137] The readable storage medium includes a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0138] A computer readable storage medium may be a tangible device that can retain and store instructions for use by an instruction execution device. A computer readable storage medium may be an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the above devices, but is not limited thereto. A non-exhaustive list of more specific examples of computer readable storage media includes: portable computer floppy disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disk read-only memory (CD-ROM), digital versatile disk (DVD), memory card, floppy disk, encoding mechanical device (such as a punch card or a groove with a raised structure with instructions recorded) and any suitable combination of the above devices. The computer readable storage medium used herein should not be understood as a transmission signal itself, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium, or an electrical signal transmitted through a wire, etc.

[0139] Figure 2 A schematic diagram of a power distribution system provided in some embodiments of the present application is shown. Figure 2 As shown, according to one embodiment of the present application, optionally, a power distribution system 200 is provided, including:

[0140] At least two distribution lines 202 are provided between the power source 201 and the load 203, wherein each distribution line 202 is provided with at least two circuit breakers 204; a distribution network complex fault detection device 500, which is provided on the distribution line and is used to control the on / off state of the circuit breaker; and a master station 205, which is connected to the distribution network complex fault detection device 500 in communication. Since the distribution network complex fault detection device 500 is the distribution network complex fault detection device in any of the above embodiments, it has all the technical effects of the distribution network complex fault detection device in any of the above embodiments, which will not be described in detail.

[0141] It should be noted that the master station 205 is used to receive information sent by the distribution network complex fault detection device 500.

[0142] like Figure 2 As shown, the power distribution system 200 includes two power distribution lines 202, each of which is provided with a plurality of circuit breakers 204, each of which is connected to a slave station, and each of which is also connected to a measuring device, which is used to collect the measured parameters at the circuit breaker 204, including but not limited to the power frequency voltage, power frequency current, current traveling wave, voltage traveling wave, etc. The plurality of slave stations are all connected to the master station 205 in communication, and the master station 205 is provided with a distribution network complex fault detection device.

[0143] like Figure 2 As shown, k1 and k2 represent two-point secondary faults.

[0144] It should be clarified that in the claims, specification and drawings of the present application, the term "multiple" refers to two or more than two. Unless otherwise clearly defined, the orientation or position relationship indicated by the terms "upper" and "lower" is based on the orientation or position relationship shown in the drawings, which is only for the purpose of more conveniently describing the present application and making the description process easier, rather than indicating or implying that the device or element referred to must have the specific orientation described, be constructed and operated in a specific orientation, so these descriptions cannot be understood as limitations on the present application; the terms "connect", "install", "fix" and the like should be understood in a broad sense. For example, "connection" can be a fixed connection between multiple objects, or a detachable connection between multiple objects, or an integral connection; it can be a direct connection between multiple objects, or an indirect connection between multiple objects through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood based on the specific circumstances of the above data.

[0145] In the claims, specification and drawings of the present application, the description of the terms "one embodiment", "some embodiments", "specific embodiments" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the claims, specification and drawings of the present application, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0146] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for detecting complex faults in a distribution network, characterized in that: Applied to a power distribution system, the power distribution system includes at least two power distribution lines, each of the power distribution lines includes at least two circuit breakers, and the complex fault detection method of the distribution network includes: When the zero-sequence voltage of the power distribution system is greater than a first voltage threshold, obtaining voltage traveling waves and current traveling waves in at least two power distribution lines; Determining the polarity relationship between the voltage traveling wave and the current traveling wave in each of the power distribution lines; Determine the distribution lines with opposite polarity as single-phase grounding fault lines, and determine the distribution lines with the same polarity as sound lines; When the zero-sequence voltage of the power distribution system is less than or equal to the first voltage threshold, obtaining power frequency current and power frequency voltage in at least two distribution lines, and operation information of at least two circuit breakers; When the power frequency current is greater than the current threshold, and the power frequency voltage is less than the second voltage threshold, and the first circuit breaker and the second circuit breaker of at least two of the circuit breakers perform a timed tripping action, it is determined that the distribution line is in a phase-to-phase short circuit fault; The distribution section between the first circuit breaker and the second circuit breaker is determined as a phase-to-phase short circuit fault section, wherein the first circuit breaker is the circuit breaker close to the power supply side of the phase-to-phase short circuit fault section, and the second circuit breaker is the circuit breaker close to the load side of the phase-to-phase short circuit fault section.

2. The method for detecting complex faults in a distribution network according to claim 1, characterized in that: The first circuit breaker and the second circuit breaker of the at least two circuit breakers perform a timed tripping action, comprising: When the power frequency current is greater than the current threshold and the power frequency voltage is less than the second voltage threshold, the first circuit breaker trips after a delay of a preset time length; After the first circuit breaker trips after a preset delay time, the second circuit breaker trips.

3. The method for detecting complex faults in a distribution network according to claim 2, characterized in that: The preset time lengths of the action delays of at least two of the circuit breakers from the load side to the power side are increased in sequence.

4. The method for detecting complex faults in a distribution network according to any one of claims 1 to 3, characterized in that: After determining the distribution lines with opposite polarity as single-phase grounding fault lines and determining the distribution lines with the same polarity as sound lines, the distribution network complex fault detection method further includes: Obtaining the arrival time of the initial fault traveling wave to each of the circuit breakers in the single-phase grounding fault line; A single-phase grounding fault section in the single-phase grounding fault line is determined according to the arrival time.

5. The method for detecting complex faults in a distribution network according to any one of claims 1 to 3, characterized in that: Determining the polarity relationship between the voltage traveling wave and the current traveling wave in each of the power distribution lines comprises: In the case where the voltage traveling wave and the current traveling wave satisfy a first relational expression, it is determined that the polarity relationship between the voltage traveling wave and the current traveling wave is opposite in polarity, and the first relational expression includes: Among them, i Fα 、i Fβ are the initial line mode current traveling waves on the single-phase grounding fault line, i F0 is the initial zero-mode current traveling wave on the single-phase grounding fault line, u Fα 、u Fβ They are all the initial line mode voltage traveling waves on the single-phase grounding fault line, u F0 is the initial zero-mode voltage traveling wave on the single-phase grounding fault line, n is the number of lines, R f is the transition resistance, u AF is the voltage at the fault point before the fault occurs, Z α is the traveling wave impedance of the line mode, and Z0 is the traveling wave impedance of the zero mode.

6. The method for detecting complex faults in a distribution network according to any one of claims 1 to 3, characterized in that: Determining the polarity relationship between the voltage traveling wave and the current traveling wave in each of the power distribution lines comprises: In the case where the voltage traveling wave and the current traveling wave satisfy a second relational expression, it is determined that the polarity relationship between the voltage traveling wave and the current traveling wave is the same polarity, and the second relational expression includes: Among them, i Nα 、i Nβ are the initial line mode current traveling waves on a sound line, i N0 is the initial zero-mode current traveling wave on a sound line, u Nα 、u Nβ are the initial line mode voltage traveling waves on a sound line, u N0 is the initial zero-mode voltage traveling wave on a sound line, n is the number of lines, R f is the transition resistance, u AF is the voltage at the fault point before the fault occurs, Z α is the traveling wave impedance of the line mode, and Z0 is the traveling wave impedance of the zero mode.

7. The method for detecting complex faults in a distribution network according to any one of claims 1 to 3, characterized in that: The value range of the first voltage threshold is 5% to 15% of the rated voltage value.

8. A complex fault detection device for a distribution network, characterized in that: Applied to a power distribution system, the power distribution system includes at least two power distribution lines, each of the power distribution lines includes at least two circuit breakers, and the distribution network complex fault detection device includes: An acquisition module, configured to acquire voltage traveling waves and current traveling waves in at least two distribution lines when the zero-sequence voltage of the distribution system is greater than a first voltage threshold; A determination module, used to determine the polarity relationship between the voltage traveling wave and the current traveling wave in each of the distribution lines; The determination module is further used to determine the distribution lines with opposite polarity as single-phase grounding fault lines, and determine the distribution lines with the same polarity as sound lines; The acquisition module is further configured to acquire power frequency current and power frequency voltage in at least two distribution lines and action information of at least two circuit breakers when the zero-sequence voltage of the power distribution system is less than or equal to the first voltage threshold; The determination module is further configured to determine that the distribution line is in a phase-to-phase short circuit fault when the power frequency current is greater than a current threshold, the power frequency voltage is less than a second voltage threshold, and a first circuit breaker and a second circuit breaker of at least two of the circuit breakers perform a timed tripping action; The determination module is also used to determine the distribution section between the first circuit breaker and the second circuit breaker as a phase-to-phase short circuit fault section, wherein the first circuit breaker is the circuit breaker close to the power supply side of the phase-to-phase short circuit fault section, and the second circuit breaker is the circuit breaker close to the load side of the phase-to-phase short circuit fault section.

9. A complex fault detection device for a distribution network, characterized in that: Also includes: processor; A memory, wherein a program or instruction is stored in the memory, and the processor implements the steps of the complex fault detection method for the distribution network as described in any one of claims 1 to 7 when executing the program or instruction in the memory.

10. A power distribution system, characterized in that: include: At least two power distribution lines are arranged between the power source and the load, wherein each of the power distribution lines is provided with at least two circuit breakers; The complex fault detection device for distribution network according to claim 8 or 9, wherein the complex fault detection device for distribution network is arranged on the distribution line, and the complex fault detection device for distribution network is used to control the on-off state of the circuit breaker; The main station is communicatively connected with the distribution network complex fault detection device.

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